Don't spend tons of money doing this.
There is a really slick, cheap and easy way to put good music in your car that won't eat your dash, glovebox or anything else in the interior of your car.
Go on eBay or craigslist.
Look for a preamped equalizer. 200watts is plenty. You'll spend about $30.
Run ignition source power to the equalizer, run your speakers to it (I ran speakers to a 2 channel potentiometer/ volume knob in place of the electronics of my "speaker" knob I use on the bottom of the dash for on the fly volume control) and run an input jack extension from the back of the equalizer to some place under the dash or your choice to plug into. I put the equalizer under the package tray, by the speakers. They are about the size of a stereo deck, or smaller and you can get great quality and perfect equalization to tune it to the cabin of the car, for good sound.
At that point, you can plug anything into the input jack, from the headphone jack of your portable music player (anything from a portable 8 track to mp3 player of any make will work.)
No more butchered dash, no expensive conversions, no reaching across the dash to a constantly open glovebox, no old wiring, no music to get scratched up, lost, stolen or damaged if you use an MP3 player and take it out of the car.
I'll never put another car stereo in anything. I get AM from the original radio and the MP3 player I have, has FM if I want it.